This invention relates generally to an illuminator, and more particularly to a spotlight or floodlight type of illuminator, as is typically used for theatrical lighting. Due to the artistic nature of the medium, it is desirable to have a versatile illuminator which provides a wide range of illumination effects, such as flat and peak fields, soft and sharp field edges, a variety of field angles or beam spreads, a variety of illumination intensities at the same distance, the ability to shape the field or project patterns, and the ability to color the light output. It is further desirable to accomplish all of these variations quickly and manually without the need for special tools or additional illuminators.
Such lights usually include a housing, illumination source and reflector, and one or more lenses. They may additionally include shutter blades, pattern grids, or an iris in the vicinity of the lens focal point to shape the light output or control its intensity. Color filter gels may be used where convenient.
In the past, the lamps used in these illuminators were relatively large because of the large filaments or discharge areas necessary to produce sufficient light output. Incandescent lamps contained a lengthy filament supported to form a large grid, and discharge lamps contained a lengthy discharge area between electrodes. While the position of the actual illumination source with respect to the spotlight optics was important, due to the large size of the source, position was not as crucial as it is today with smaller sources, such as HMI lamps and smaller, higher output incandescent lamps. For instance, see U.S. Pat. No. 2,114,963 issued to J. Levy in 1938, which discloses a lamp that is firmly positioned with no means for adjustment.
As illumination sources became more compact and approached a more ideal point source, their position within the illuminator became more critical and adjustment was necessary to optimize the light output of the spotlight optical system and desirable to achieve a variety of other illumination characteristics or effects. Such a positioning means is disclosed in U.S. Pat. No. 4,061,912 issued to Levasseur, but it is more complex than the present invention, and demands exacting techniques to manufacture and position a spherical rear wall having its geometric center at the center of the reflector access opening.
Moveable lenses are disclosed in U.S. Pat. No. 2,114,963 issued to Levy, U.S. Pat. No. 2,650,292 issued to Strong, U.S. Pat. No. 3,116,022 issued to Davis, and U.S. Patent Application Ser. No. 739,694, filed Nov. 8, 1976, and assigned to the present applicants' assignee. However, each of these patents discloses lenses in a fixed or predetermined relationship with one another, the lamp, or both. Therefore, in order to change the focal length or field angle, or alter the light output or illumination characteristics of these devices, it is necessary to dismantle the spotlight and purchase another spotlight or optical system.